Apparatus and Integrated Process for Separating a Mixture of Carbon Dioxide and at Least One Other Gas and for Separating Air by Cryogenic Distillation

ABSTRACT

An integrated apparatus for separating a mixture of carbon dioxide and at least one other gas and for separating air by air distillation is provided. The apparatus includes a CO 2  separation unit configured to separate the mixture, an air separation unit configured to separate air by cryogenic distillation, a water cooling tower that operates by direct contact, a line for sending water to the top of the tower, a line for sending at least one portion of the nitrogen-enriched gas stream to a lower level of the tower, a cooled water line for withdrawing cooled water from the tower and means for cooling the air upstream of the air separation unit, the cooled water line being connected to means for cooling the air upstream of the air separation unit and to the inlet and/or to the outlet of the unit for separating the gaseous mixture.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a §371 of International PCT ApplicationPCT/FR2012/051203, filed May 29, 2012, which claims the benefit ofFR1154754, filed May 31, 2011, both of which are herein incorporated byreference in their entireties.

TECHNICAL FIELD OF THE INVENTION

This invention relates to an apparatus and integrated process forseparating a mixture of carbon dioxide and at least one other gas andfor separating air by cryogenic distillation.

It relates in particular to an apparatus and integrated process forseparating a mixture of carbon dioxide and at least one other gas andfor separating air by cryogenic distillation, with water coolingintended to cool the mixture and/or the air upstream of the separation.

BACKGROUND

Compression and purification apparatuses treating supplies that are richin CO₂ (more than 35% volume on a dry basis, preferably more than 70%)produce in essence a flow with less CO₂ content than the supply andcontaining the gases that will have been extracted from the product. Thepurification of the CO₂ can take place thanks to one or several partialcondensation(s) or by membrane separation or any other process(adsorption, cryo-condensation, etc.). In certain processes such asthose mentioned, the flow of impure gas is a dry product. This will notbe the case for a separation by scrubbing with amines for example,wherein the two products of the separation (the CO₂ and the residualgases) will be wet.

Most CO₂ treatment units include a step of drying the gases treated.This can be drying via adsorption. A dry gas must then be used toregenerate the adsorbent when it is saturated with water. The state ofthe art provides as such to use the gases vaporised from the storage ofCO₂ or residual gases, at high or low pressure.

It is known from EP-A-1712858 to use a carbon dioxide depleted gas tocool the water in a water cooling tower.

EP-A-0503190 discloses a water cooling system for an apparatus forseparating a mixture of carbon dioxide, oxygen and nitrogen wherein awater cooling tower is supplied with expanded nitrogen coming from anapparatus for separating air and water, with the cooled water then beingused to cool the mixture to be separated. Before it is sent to thetower, the nitrogen is sent to the top condenser of a distillationcolumn and then to the cooling exchanger of the mixture to be separated.This complicated arrangement requires the presence of a turbine so thatthe nitrogen has enough refrigeration to supply the required cold.Nothing makes it possible to think that this cold would be sufficient tocool both the water for the apparatus for separating the mixture and theapparatus for separating air.

SUMMARY OF THE INVENTION

In certain embodiment, the invention proposes, according to certainalternatives, another use for the dry residual gases. They can as suchbe saturated with water in a tower that operates by direct contact,making it possible as such to lower the temperature of the unevaporatedwater and produce chilled water. The method is commonly used on theapparatuses for separating air in “water-nitrogen towers” in order tocool the water by heat exchange and evaporation with the cold nitrogencoming from the apparatus for separating air.

For the case where the incondensable items have a flow rate relative tothe total flow treated that is clearly lower than nitrogen in relationto the air, a first portion of the cooling of the water could be carriedout in a “non-condensable water” tower, with the first portion of thecooling being supplemented by a second portion of cooling in arefrigeration unit.

When an apparatus for separating air having a water cooling towerlocated in the vicinity of an apparatus for separating a mixture ofcarbon dioxide and at least one other gas, using the water-nitrogentower in order to produce cold water for the two apparatuses and alsopossibly saturating therein the incondensable items (which will thenshare the venting of the nitrogen) will allow for genuine gains ininvestment in relation to using two independent towers.

The CO₂ contained in the incondensable items must be prevented at allcost from rising back up to the apparatus for separating air via theline for transferring the dry nitrogen to the water-nitrogen tower. Innormal operation as in the case of degraded mode, there is a real riskof introducing CO₂ into the apparatus for separating air and of cloggingit when the CO₂ has frozen.

It can as such be considered to introduce the CO₂ at a second level inthe tower, above the nitrogen.

Note however that the risk is similar to that of allowing moisture toenter the cold box of the apparatus for separating air, except in thatthe incondensables arrive under pressure whereas when the nitrogen hasbecome wet, it necessarily is at a pressure that is lower than at whichit was in the box since it comes from there.

A precautionary measure, which is claimed as inventive also, consists inexpanding the incondensable items sufficiently far from the tower sothat over a distance that will be deemed as reasonable, the pressure inthe supply pipe of the tower is lower for the line of incondensableitems than for the line of nitrogen.

According to a particularly simple alternative, the process consists incooling the water by using nitrogen from an ASU and possibly at leastone gas coming from a unit for separating a mixture of CO₂ and at leastone other gas, which can for example be nitrogen, oxygen, argon, carbonmonoxide, hydrogen, methane, NO₂ or a mixture of at least two of thesegases.

According to an object of the invention, an integrated apparatus isprovided for separating a mixture of carbon dioxide and at least oneother gas and for separating air by air distillation comprising a unitfor separating a gaseous mixture comprising carbon dioxide at and leastone other gas in order to produce a carbon dioxide-enriched gas and acarbon dioxide depleted gas and a unit for separating air by cryogenicdistillation in order to produce at least one nitrogen-enriched gasstream characterised in that it comprises a water cooling tower thatoperates by direct contact as well as a line for sending water to thetop of the tower, a line for sending at least one portion of thenitrogen-enriched gas stream to a lower level of the tower, a cooledwater line for withdrawing cooled water from the tower and means forcooling the air upstream of the air separation unit, the cooled waterline being connected to means for cooling the air upstream of the airseparation unit and to the inlet and/or to the outlet of the unit forseparating the gaseous mixture.

According to other optional aspects of the invention:

-   -   the means for cooling the air upstream of the air separation        unit are constituted of a water cooling tower and a line for        sending heated water from the scrubbing tower to the water        cooling tower;    -   the cooled water line is adapted to send cooled water from the        tower to the unit for separating the mixture in order to provide        refrigeration to the gaseous mixture to be separated and/or to a        product of the separation;    -   the integrated apparatus comprises an oxy-fuel combustion unit,        a line for sending the oxygen from a (from the) apparatus for        separating air to the oxy-fuel combustion unit and a line for        sending fumes from the oxy-fuel combustion to the unit for        separating a mixture as a gaseous mixture;    -   the apparatus comprises a line for sending the carbon dioxide        depleted gas to the water cooling tower and wherein possibly the        level of introduction of the nitrogen-enriched gas stream is        lower than the level of the tower to which the carbon dioxide        depleted gas is sent;    -   the apparatus comprises a mechanical refrigeration unit in order        to cool the water cooled in the cooling tower upstream of the        means for cooling the air upstream of the air separation unit        and/or before it is sent to the unit for separating the gaseous        mixture.

According to another object of the invention, an integrated process isprovided for separating a mixture of carbon dioxide and at least oneother gas and for separating air by air distillation comprising a unitfor separating a gaseous mixture comprising carbon dioxide and at leastone other gas in order to produce a carbon dioxide-enriched gas and acarbon dioxide depleted gas and a unit for separating air by cryogenicdistillation in order to produce at least one nitrogen-enriched gasstream characterised in that water is cooled in a water cooling towerthat operates by direct contact with the nitrogen-enriched gas stream,the air intended for the air separation unit is cooled with the cooledwater in the cooling tower and the gaseous mixture intended for the unitfor separating the gaseous mixture and/or a product from the unit forseparating the gaseous mixture is cooled using the cooled water comingfrom the cooling tower.

According to other optional aspects:

-   -   the air is cooled upstream of the air separation unit in a        scrubbing tower with water supplied by water cooled in the water        cooling tower;    -   oxygen from one (from the) apparatus for separating air is sent        to an oxy-fuel combustion unit and fumes from the oxy-fuel        combustion are sent to the unit for separating a mixture as a        gaseous mixture;    -   carbon dioxide depleted gas is sent from the unit for separating        the gaseous mixture in the water cooling tower;    -   the level of introduction of the nitrogen-enriched gas stream is        lower than the level of the tower where the carbon dioxide        depleted gas is sent;    -   the water cooled in the cooling tower is cooled by means of a        mechanical refrigeration unit, upstream of the means for cooling        the air upstream of the air separation unit and upstream of the        unit for separating the gaseous mixture;    -   the carbon dioxide depleted gas is expanded in a valve to a        pressure that is lower than that at which the nitrogen-enriched        gas stream is introduced in the water cooling tower;    -   at least one other gas in the mixture is nitrogen, oxygen,        argon, hydrogen, carbon monoxide, methane or NO₂ and the mixture        contains at least 40 mol. % of carbon dioxide;    -   at least one other gas in the mixture is chosen from the list        comprising hydrogen, carbon monoxide or methane and a wet gas        exiting the top of the water cooling tower is used as a fuel,        for example in a gas turbine;    -   the unit for separating the gaseous mixture separates the        mixture by distillation and/or phase separation at sub-ambient        temperature.

According to another object of the invention, an integrated apparatus isprovided for separating a mixture of carbon dioxide and at least oneother gas and for separating air by air distillation comprising a unitfor separating a gaseous mixture comprising carbon dioxide and at leastone other gas in order to produce a carbon dioxide-enriched gas and acarbon dioxide depleted gas and an air separation unit by cryogenicdistillation in order to produce at least one nitrogen-enriched gasstream characterised in that it comprises a water cooling tower thatoperates by direct contact as well as a line for sending water to thetop of the tower, a line for sending carbon dioxide depleted gas to alower level of the tower, a line for sending at least one portion of thenitrogen-enriched gas stream to a lower level of the tower, a cooledwater line for withdrawing cooled water from the tower, means forcooling the air upstream of the air separation unit, the cooled waterline being connected to the means for cooling the air upstream of theair separation unit.

According to other optional aspects:

-   -   the means for cooling the air upstream of the air separation        unit are constituted of a scrubbing tower with water and a line        for sending heated water from the scrubbing tower to the water        cooling tower;    -   the apparatus comprises a line for sending cooled water from the        tower to the unit for separating the mixture in order to provide        refrigeration;    -   the apparatus comprises an apparatus such as described        hereinabove comprising an oxy-fuel combustion unit, a line for        sending oxygen from an apparatus for separating air to the        oxy-fuel combustion unit and a line for sending fumes from the        oxy-fuel combustion to the unit for separating a mixture as a        gaseous mixture;    -   the nitrogen-enriched gas stream is sent to a level of the water        cooling tower that is lower than that at which the carbon        dioxide depleted gas is sent;    -   the line for sending at least one portion of the        nitrogen-enriched gas stream from the air separation unit is        connected to the lower level of the tower without passing        through a turbine or an exchanger intended to cool the gaseous        mixture.

According to another objet of the invention, an integrated process isprovided for separating a mixture of carbon dioxide and at least oneother gas and for separating air by air distillation in an installationcomprising a unit for separating a gaseous mixture comprising carbondioxide and at least one other gas in order to produce a carbondioxide-enriched gas and a carbon dioxide depleted gas and a unit forseparating air by cryogenic distillation in order to produce at leastone nitrogen-enriched gas stream characterised in that the installationcomprises a water cooling tower that operates by direct contact as wellas a line for sending water to the top of the tower, and wherein carbondioxide depleted gas is sent to a lower level of the tower, at least oneportion of the nitrogen-enriched gas stream is sent to a lower level ofthe tower, cooled water is withdrawn from the tower, the air is cooledin means in order to cool the air upstream of the air separation unitand cooled water is sent from the tank of the tower to the means forcooling the air upstream of the air separation unit.

According to other optional characteristics:

-   -   the air upstream of the air separation unit is cooled by direct        exchange with cooled water coming from the water cooling tower;    -   the cooled water is sent from the water cooling tower to the        unit for separating the mixture in order to provide        refrigeration either upstream or downstream of the separation,        with the water being taken either upstream or downstream of a        mechanical refrigeration unit of the water cooled in the water        cooling tower;    -   the carbon dioxide depleted gas is expanded in a valve to a        pressure lower than that at which the nitrogen-enriched gas        stream is introduced in the water cooling tower;    -   at least one other gas in the mixture is nitrogen, oxygen,        argon, hydrogen, carbon monoxide, methane or NO₂ and the mixture        contains at least 40 mol. % of carbon dioxide;    -   at least one other gas comprises hydrogen, carbon monoxide or        methane and a wet gas exiting the top of the water cooling tower        is used as a fuel, for example in a gas turbine;    -   the nitrogen-enriched stream is sent from the apparatus for        separating air to the tower without having been expanded and        without having been heated in a cooling exchanger of the gaseous        mixture;    -   the operating pressure of the tower is substantially equal to        the pressure at which the nitrogen exits the apparatus for        separating air.

An advantage of this invention is that it allows for the integration ofproduction of cold water for apparatuses for separating with as the onlyconnection between the two apparatuses a cooled water line, although asolution according to prior art requires a nitrogen line under pressurethat connects the two apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, claims, and accompanying drawings. It is to be noted,however, that the drawings illustrate only several embodiments of theinvention and are therefore not to be considered limiting of theinvention's scope as it can admit to other equally effectiveembodiments.

FIG. 1 shows an embodiment of the invention.

FIG. 2 shows an embodiment of the invention.

FIG. 3 shows an embodiment of the invention.

FIG. 4 shows an embodiment of the invention.

DETAILED DESCRIPTION

The invention shall be described in more detail by referring to thefigures.

FIG. 1 shows an apparatus and an integrated process for separating amixture of carbon dioxide and at least one other gas and for separatingair by cryogenic distillation according to the invention. FIGS. 2 to 4show the details of various water cooling towers used to cool the airupstream of the air separation by distillation in FIG. 1, according tothe invention. In FIG. 1, a stream of air 1 is cooled in a pre-coolingunit P comprising an air scrubbing tower with water and a water coolingtower with nitrogen 17. This type of cooling is well known in the“Industrial Gas Handbook” by F. G. Kerry, page 112. The air 3 cooled inthe pre-cooling unit P is sent to an apparatus for separating air ASUwherein it is purified in order to remove the carbon dioxide and themoisture, cooled and separated in a system of columns in order toproduce oxygen 5 and nitrogen 17. The oxygen 5 is sent to an oxy-fuelcombustion boiler B also supplied with fuel 7. Fumes 9 coming from theoxy-fuel combustion unit B contain at least 40 mol. % of carbon dioxideon a dry basis, or even at least 60 mol. % of carbon dioxide, and atleast one component chosen from the following list: nitrogen, oxygen,argon, hydrogen, carbon monoxide, methane or NO₂. The fumes are treatedin a separating unit CPU. Upstream of the CPU, the fumes 9 are cooled ina cooling unit R by heat exchange with cold water 15. The fumes arepossibly compressed and then separated by phase separation and/ordistillation in the unit CPU at a sub-ambient temperature. This makes itpossible to produce a carbon dioxide-enriched stream CO₂ in liquid orgaseous form 20 and a carbon dioxide depleted gas stream 13. The carbondioxide depleted stream 13 can be a stream of nitrogen, oxygen, argon orNO₂ or a mixture of at least two of these gases. The stream 13 exits theunit CPU at a temperature close to ambient temperature (−10° C. to 80°C.) and a pressure close to atmospheric pressure (1 bar a to 2 bars a)and is expanded in a valve V at a pressure of a few tens to a fewhundred millimetres of water column according to load losses of thesystem downstream. The expanded gas 13 can be sent to pre-cooling.

The nitrogen 17 is sent directly from the apparatus for separating airASU to the pre-cooling unit P without passing through another means oftreatment, such as a turbine or an exchanger other than the air coolingexchanger associated with the apparatus for separating air ASU.

The pre-cooling unit produces cold water which is sent either to theunit R as a stream 15 or is used in the unit P or both.

FIG. 2 shows detail of the pre-cooling unit P.

This unit comprises a cooling tower 33 wherein the water 31 comes intodirect contact with nitrogen 17 coming from the apparatus for separatingair ASU. The expanded gas 13 can be sent to the tower at a level higherthan the inlet level of the nitrogen 17, possibly separated from theinlet level of the nitrogen by a lining stage. The nitrogen 17 comesfrom the apparatus ASU directly and arrives in the tower 33 withoutpassing through the elements R or CPU.

The water cooling tower 33 is supplied at the top by a stream of water31 at a temperature from 4° C. to 40° C. The pressure of the stream 13is slightly less than that of the stream 17 at the inlet in the tower33, thanks to the expansion in the valve V upstream of the tower, inorder to prevent polluting the cooled water.

The gas 17 and possibly the gas 13 cool the water by direct contact andevaporation of a portion of the water in these dry gases and the mixtureformed 39 exits at the top of the tower as venting. The water heated inthe unit CPU can be sent back to the unit P via the supply 21.

The cooled water in the tank of the tower 33 is pumped by a pump 25 inorder to be sent to the air cooling tower with water by the line 27.Otherwise the cooled water can be sent to an exchanger with indirectcontact in order to transfer refrigeration to the air intended for thedistillation. A portion of this water 27 can also be used to providerefrigeration to the unit CPU, for example upstream of the desiccationunit.

This process may possibly not use a mechanical refrigeration unit suchas a refrigeration unit. The tower 33 will possibly be somewhat largerthan that used solely for providing water for the air separation unitASU.

For the processes of FIGS. 3 and 4, a refrigeration unit 35 is used. Inthis way, instead of having a refrigeration unit for each of the units,a single refrigeration unit can cool the air separation unit ASU and theunit for separating the mixture containing carbon dioxide CPU.

FIG. 3 shows detail of the pre-cooling unit P.

This unit P comprises a cooling tower 33 wherein the water 31 comes intocontact direct with nitrogen 17 coming from the apparatus for separatingair ASU and an air cooling tower with water 133. The expanded gas 13 ispossibly sent to the tower 33 at a level higher than the inlet level ofthe nitrogen 17. The nitrogen 17 comes from the apparatus ASU directlyand arrives in the tower 33 without passing through the elements R orCPU.

The water cooling tower 33 is supplied at the top by a stream of water31 at a temperature from 10° C. to 50° C.

The pressure of the stream 13 is slightly less than that of the stream17 at the inlet in the tower 33, thanks to the expansion in the valve Vupstream of the tower. The operating pressure of the tower 33 issubstantially equal to the pressure at which the nitrogen 17 exits theapparatus for separating air ASU.

The gas 17 and possibly the gas 13 cool the water by direct contact andevaporation and the mixture formed 39 exits at the top of the tower asventing.

The cooled water in the tank of the tower 33 is pumped by a pump 25 inorder to be sent to the top of the air cooling tower with water 133 as astream 37. The air 1 intended for the distillation is cooled by beingsent to the tank of the tower 133. The cooling water 21 is sent to anintermediate level of the tower 133 as a stream 121 and to the top ofthe tower 33 as a stream 31. The water cools the air by producing, atthe top of the tower 133, a stream of cooled air 3 which is sent forpurification and then for distillation in the air separation unit ASU.

The heated water 221 is collected in the tank of the tower 133 and isrecycled in the tower 133 after exterior refrigeration (by using aircoolers, through exchange with cold water, etc.). It can also beconsidered that the water 221 is not recycled but returns, for example,to a river or a water network downstream.

The cooled water 23 collected in the tank of the tower 33 is pressurisedby the pump 25 and a portion 15 is sent to the separation unit CPU. Therest of the water is cooled by a refrigeration unit 35 in order toconstitute the stream 37 sent to the top of the tower 133.

FIG. 4 differs from FIG. 3 only in that all of the water coming from thepump 25 is cooled in the refrigeration unit before it is divided intotwo. The cooled stream 37 is sent to the top of the tower 133 and thecooled stream 15 is sent to the unit CPU.

The cooled water 15 sent to the CPU can be used to cool the mixture tobe separated or to cool a product from the separation. The unit CPU doesnot necessarily operate at sub-ambient temperature. The water heated inthe unit CPU can be sent to the unit P via the supply 21.

The apparatus for separating air ASU does not necessarily supply anoxy-fuel combustion unit, if present, with oxygen. It is sufficient forthe apparatus for separating air ASU to be located relatively close tothe unit CPU to allow for the integration between the two.

For the case wherein the carbon dioxide depleted gas comprises carbonmonoxide and/or methane and/or hydrogen, the gas can be sent to thecooling tower and the wet gas formed at the top of the tower can be usedas a fuel, for example in a gas turbine.

While the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace all such alternatives, modifications, and variations as fallwithin the spirit and broad scope of the appended claims. The presentinvention may suitably comprise, consist or consist essentially of theelements disclosed and may be practiced in the absence of an element notdisclosed. Furthermore, if there is language referring to order, such asfirst and second, it should be understood in an exemplary sense and notin a limiting sense. For example, it can be recognized by those skilledin the art that certain steps can be combined into a single step.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

“Comprising” in a claim is an open transitional term which means thesubsequently identified claim elements are a nonexclusive listing (i.e.,anything else may be additionally included and remain within the scopeof “comprising”). “Comprising” as used herein may be replaced by themore limited transitional terms “consisting essentially of” and“consisting of” unless otherwise indicated herein.

“Providing” in a claim is defined to mean furnishing, supplying, makingavailable, or preparing something. The step may be performed by anyactor in the absence of express language in the claim to the contrary arange is expressed, it is to be understood that another embodiment isfrom the one.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such particular valueand/or to the other particular value, along with all combinations withinsaid range.

All references identified herein are each hereby incorporated byreference into this application in their entireties, as well as for thespecific information for which each is cited.

1-15. (canceled)
 16. An apparatus for separating a mixture of carbondioxide and at least one other gas and for separating air by airdistillation, the apparatus comprising: a CO₂ separation unit configuredto separate a gaseous mixture comprising carbon dioxide and at least oneother gas in order to produce a carbon dioxide-enriched gas and a carbondioxide depleted gas; an air separation unit (ASU) configured toseparate air by cryogenic distillation in order to produce at least onenitrogen-enriched gas stream; and a water cooling tower that operates bydirect contact as well as a line for sending water to the top of thewater cooling tower, a line for sending at least one portion of thenitrogen-enriched gas stream to a lower level of the water coolingtower, a cooled water line for withdrawing cooled water from the watercooling tower and means for cooling the air upstream of the airseparation unit, the cooled water line being connected to means forcooling the air upstream of the air separation unit and to the inletand/or to the outlet of the CO₂ separation unit.
 17. The apparatus asclaimed in claim 16, wherein the means for cooling the air upstream ofthe ASU comprises a scrubbing tower with water.
 18. The apparatus asclaimed in claim 17, wherein the means for cooling the air upstream ofthe ASU further comprises a line configured to send heated water fromthe scrubbing tower to the water cooling tower.
 19. The apparatus asclaimed in claim 16, wherein the cooled water line is configured to sendcooled water from the tower to the CO₂ separation unit such thatrefrigeration is provided to the gaseous mixture to be separated or to aproduct from the separation.
 20. The apparatus as claimed in claim 16,further comprising an oxy-fuel combustion unit, a line for sendingoxygen from the ASU to the oxy-fuel combustion unit and a line forsending fumes from the oxy-fuel combustion to the CO₂ separation unit .21. The apparatus as claimed in claim 16, further comprising a lineconfigured to send the carbon dioxide depleted gas to the water coolingtower and wherein possibly the level of introduction of thenitrogen-enriched gas stream is lower than the level of the tower wherethe carbon dioxide depleted gas is sent.
 22. The apparatus as claimed inclaim 16, further comprising a mechanical refrigeration unit configuredto cool the water cooled in the cooling tower upstream of the means forcooling the air upstream of the ASU and/or before it is sent to the CO₂separation unit.
 23. The apparatus as claimed in claim 16, wherein theline for sending at least one portion of the nitrogen-enriched gasstream from the ASU is connected to a lower level of the tower withoutpassing through a turbine or an exchanger configured to cool the gaseousmixture.
 24. An integrated process for separating a mixture of carbondioxide and at least one other gas and for separating air by airdistillation, comprising a CO₂ separation unit configured to separate agaseous mixture comprising carbon dioxide and at least one other gas toproduce a carbon dioxide-enriched gas and a carbon dioxide depleted gasand an air separation unit by cryogenic distillation in order to produceat least one nitrogen-enriched gas stream wherein the water is cooled ina water cooling tower that operates by direct contact with thenitrogen-enriched gas stream, the air intended for the air separationunit is cooled with water cooled in the cooling tower and the gaseousmixture intended for the CO₂ separation unit and/or a product from theCO₂ separation unit is cooled using the cooled water coming from thecooling tower.
 25. The process as claimed in claim 24, wherein the airupstream of the air separation unit is cooled in a scrubbing tower withwater supplied by water cooled in the water tooling tower.
 26. Theprocess as claimed in claim 24, further comprising the steps of sendingthe oxygen from the ASU to an oxy-fuel combustion unit; and sendingfumes from the oxy-fuel combustion to the CO₂ separation unit.
 27. Theprocess as claimed in claim 24, further comprising sending carbondioxide depleted gas from the CO₂ separation unit to the water coolingtower,
 28. The process as claimed in claim 27, wherein the level ofintroduction of the nitrogen-enriched gas stream is lower than the levelof the tower where the carbon dioxide depleted gas is sent.
 29. Theprocess as claimed in claim 24, wherein the cooled water is cooled inthe cooling tower by means of a mechanical refrigeration unit beforesending it to the means for cooling air upstream of the air separationunit and/or before sending it to the CO₂ separation unit.
 30. Theprocess as claimed in claim 24, wherein the carbon dioxide depleted gasis expanded in a valve to a pressure lower than that at which thenitrogen-enriched gas stream is introduced in the water cooling tower.31. The process as claimed in claim 24, wherein at least one other gasin the mixture is selected from the group consisting of nitrogen,oxygen, argon, hydrogen, carbon monoxide, methane, NO₂, and combinationsthereof, and the mixture contains at least 40 mol. % of carbon dioxide.32. The process as claimed in claim 24, wherein at least one other gasin the mixture is selected from the group consisting of hydrogen, carbonmonoxide, methane, and combinations thereof, and wherein a wet gasexiting from the top of the water cooling tower is used as a fuel.